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Code of Practice on Drinking Water Sampling and Safety Plans

Issue date: 1 April 2019

Issued under the provisions of the

Environmental Public Health

(Water Suitable for Drinking) (No. 2) Regulations 2019

Singapore Food Agency

52 Jurong Gateway Road

JEM Office Tower

Singapore 608550

www.sfa.gov.sg

All rights reserved. No part of this publication shall be altered in any way without prior

written permission of the Singapore Food Agency.



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Table of Contents

Page number

Foreword 4

Acknowledgment 5

1.0 Definitions, acronyms and abbreviations 6

2.0 Water sampling plans 7

2.1 General 7

2.2 Basic water sampling plan 7

2.3 Comprehensive water sampling plan 8

2.4 Sampling plan for operational monitoring 9

2.5 Sampling frequency and parameters 10

2.6 Sampling locations and points 11

2.7 Test methods 11

2.8 Sampling protocol 11

3.0 Water safety plans 12

3.1 General 12

3.2 Methodology and key steps 12

3.3 Assemble a water safety team 12

3.4 Document and describe the system 13

3.5 Undertake a system assessment 13

3.6 Identify control measures and define monitoring of control measures 14

3.7 Verification of water safety plan 14

3.8 Develop supporting programmes 15

3.9 Prepare management procedures 15



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3.10 Establish documentation and communication procedures 16

3.11 Review of the water safety plan 16

3.12 Submission of the report of the review of water safety plan 16

3.13 Remedial and improvement measures 16

4.0 References 17

Appendix A

Parameters for operational monitoring of the quality of water suitable for drinking 18

Appendix B

Factors and hazards that should be considered during the preparation of water safety plan 22



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Foreword

The quality of drinking water for human consumption is of utmost importance in the protection

of the public health.

In order to ensure that a high standard of the quality of drinking water is maintained, preventive

measures such as the preparation and implementation of water sampling and safety plans for

water suitable for drinking play an important role in the provision of drinking water.

These plans must conform to certain standards and should meet certain requirements so that

there is a consistency in the monitoring, assessment and risk management practices adopted by

the drinking water providers.

This Code of Practice is issued pursuant to regulatory requirements prescribed in the

Environmental Public Health (Water Suitable for Drinking) (No. 2) Regulations. It is prepared

based on international guidelines such as those published by the World Health Organization,

and it aims to provide guidance to the water providers designated as “WSSP water providers”

under the Regulations, on the preparation of drinking water sampling and safety plans.

The Code of Practice will help the WSSP water providers in their continuing efforts to maintain

a high standard of the quality of the drinking water that they provide to the public in the course

of business, and thereby protect public health in Singapore.

Director-General, Food Administration

Singapore Food Agency

Singapore



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Acknowledgement

The Singapore Food Agency wishes to thank the following members of the Technical

Committee on National Drinking Water Quality Standards for providing valuable advice on

this Code of Practice.

Local members

Prof. Ong Say Leong (Chairman) National University of Singapore

Dr. Pranav S. Joshi (Secretary) Singapore Food Agency

Dr. Steven Ooi Peng Lim Ministry of Health

A/Prof. Richard Webster Nanyang Technological University

A/Prof. Hu Jiangyong National University of Singapore

A/Prof. Lye Lin Heng National University of Singapore

A/Prof. Sim Tiow Suan National University of Singapore

Dr. Lim Mong Hoo Public Utilities Board

Dr. Wong Kwok Onn Singapore Food Agency

A/Prof. Joanne Chan Sheot Harn Singapore Food Agency

Overseas members

Prof. Michael Rouse Independent consultant, UK

Dr. Joseph Cotruvo Joseph Cotruvo Associates, USA



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1.0 Definitions, acronyms and abbreviations

For the purpose of this Code of Practice, the following definitions, acronyms and abbreviations

will apply.

COP


Drinking water

Refers to water suitable for drinking, provided by water providers who

are regulated under the Environmental Public Health Act and EPH

(WSD) (No. 2) Regulations

E. coli Escherichia coli

EPH (WSD)

(No. 2)

Regulations

Environmental Public Health (Water Suitable for Drinking) (No. 2)

Regulations

Hazard

A chemical, physical, radiological or biological/microbiological agent

that has the potential to cause harm

Hazardous event

An incident or situation that can lead to the presence of a hazard (what

can happen and how)

Parameter A property, characteristic, element, contaminant, substance or organism

Ref. Reference(s) listed under section 4.0 of this COP

Risk

It is the likelihood of identified hazards causing harm in exposed

populations in a specified time frame, including the magnitude of that

harm and/or the consequences

SFA Singapore Food Agency

Water provider,

or provider

A WSSP water provider, as defined under the EPH (WSD) (No. 2)

Regulations

Water safety

plan

A water safety plan, as defined under the EPH (WSD) (No. 2)

Regulations

Water sampling

plan

A water sampling plan, as defined under the EPH (WSD) (No. 2)

Regulations

Water treatment

plant

A plant that produces piped drinking water (including waterworks)

WHO World Health Organization



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WHO Guidelines Ref. 4.0(a) of this COP

2.0 Water sampling plans

2.1 General

(a) A water sampling plan shall consist of a Basic water sampling plan, a Comprehensive

water sampling plan and a sampling plan for Operational monitoring.

(b) The number and type of water quality parameters, their frequency of monitoring and

the selection of sampling locations will depend upon the factors such as source and

raw water characteristics, type of water treatment used, site specific operational and

management practices, hazards identified during the preparation and review of water

safety plan, etc.1 These factors may differ from one water provider to another.

(c) Preparation and implementation of water sampling plan are important steps in the

development of overall strategies for monitoring and surveillance of quality of

drinking water. In addition, the water providers shall also implement measures to

review and analyse the test data, and carry out investigations into any adverse

feedback received from consumers, and conduct remedial actions if any unsatisfactory

situation is identified.

(d) Each provider shall use a template available from SFA to document the water

sampling plan. The plan will include information such as the name of provider’s

organization and contact details; identification of the site(s) and system(s) included in

the plan; date of preparation of the plan and revision number; amendment sheet;

details about Basic, Comprehensive and Operational monitoring plans; and other

applicable details mentioned in sections 2.2 to 2.8 and Appendix A, as necessary.

2.2 Basic water sampling plan

(Minimum sample numbers for verification of the microbial quality)

(a) A water provider shall prepare a Basic sampling plan to monitor E. coli2 bacteria from

the designated sampling locations. These locations may include-

1 Besides the water sampling plan as required under this COP, a provider may also implement additional

on-line and off-line water quality monitoring - for internal process control, source water characterization,

surveillance of parameters of emerging concerns, etc., as mentioned in Appendix A, to ensure quality of

drinking water provided.

2 Surveillance and verification of the microbial quality of drinking water typically includes testing for E.

coli, as E. coli is considered the most suitable indicator organism for presence of faecal contamination, due

to the large numbers in which E. coli is usually present in faecally polluted waters. Monitoring of specific

pathogens or other micro-organisms/indicator organisms may be undertaken by the provider in certain

situations, as mentioned in footnote 1 and Appendix A.



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(i) source or raw water facilities, or both;

(ii) water treatment systems;

(iii) service reservoirs or storage tanks supplying drinking water to various zones or

areas, pumping stations, blending points, master or bulk water meters3, and

other locations within the distribution network; and

(iv) sampling points within buildings or facilities (e.g. at the high level tank, or at

common areas, or premises having taps - water from which is normally used for

drinking, cooking or food preparation).

(b) The minimum frequencies of sampling drinking water from the designated locations

shall be in accordance with those stated under the Table 4.4 (namely, “Recommended

minimum sample numbers for faecal indicator testing in distribution systems”) of the

WHO Guidelines4. The frequency of sampling water from other designated locations

may vary depending upon the findings of risk assessment carried out under the water

safety plan.

(c) The number of samples to be collected shall be spread throughout the year, as much

as possible in the sampling plan. Thus if 12 samples are planned per year from a

designated location, the frequency should ideally be set at 1 sample per month.

2.3 Comprehensive water sampling plan

(a) The Comprehensive water sampling plan shall include the following.

(i) Subject to paragraph 2.3(c) and (d), all the water quality parameters specified

under the Schedule of the EPH (WSD) (No. 2) Regulations, except those

parameters mentioned in paragraph 2.2(a);

(ii) Other parameters5, which are identified in the water safety plan, or those that

have been monitored historically by the provider as part of surveillance to

maintain consumer confidence or address unknown contaminants (including

those mentioned in section 2.4), or those parameters that are identified as

emerging concerns due to availability of any new information or change in the

3 Where sampling points at the master water meter are not available, water can be sampled from a

downstream location for assessment of water quality, notwithstanding the fact that a provider may not be

responsible for deterioration of drinking water quality if it arises due to water service installations owned or

maintained by the management of the building or facility to which the water is provided.

4 Where data on estimated population served are not available, the provider may use the data on Singapore's

per capita domestic water consumption or such other information, and may exclude the quantity of water

used for non-potable applications, in order to determine the frequency of sampling.

5 Some of these parameters may also include those that are mentioned in Appendix A.



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pollutant sources in source water or site specific conditions (e.g. before the next

review of the water safety plan).

(b) Sample(s) shall be collected at each entry point to the distribution system or from such

locations where the drinking water is representative of its quality after the treatment.

However, where the need for additional monitoring of the entire water supply system

is identified, e.g. based on the factors mentioned under paragraph 2.3(a)(ii), other

sampling locations mentioned under paragraph 2.2(a) will also be included in the

comprehensive monitoring plan.

(c) The default frequency of sampling shall be at least once a year, except for certain

parameters that should be monitored more frequently based on relevant factors; e.g.

those mentioned in paragraph 2.3(a)(ii). Examples of parameters that may be

monitored more frequently include - boron for desalination membrane treatment

plants, disinfection by-products for water supply systems with extensive distribution

network, heavy metals and pesticides if the raw water for a traditional water treatment

system is obtained from a source that is likely to be polluted by industrial or

agricultural discharge, etc.

(d) Depending upon the raw water quality, water treatment programme, and the type of

distribution network used by the providers, it is expected that certain parameters or

contaminants are unlikely to be present in the drinking water, or will be present only

at concentrations much lower than the standards prescribed for quality of drinking

water. Hence, the water provider may propose sampling frequencies for certain

parameters that are lower than the default frequency, or may propose not to sample

the drinking water for specific parameters/contaminants that are not of concern.

(e) In doing so, the water provider shall take into consideration the following, but not

limiting to:

(i) The nature and quality of the source water, and the type of the water treatment

used.

(ii) Test results of three successive years showing that the concentration of the

parameter is significantly lower than the water quality standards prescribed

within the Schedule of the EPH (WSD) (No. 2) Regulations, and that the quality

of drinking water is unlikely to deteriorate.

(iii) The type of pesticides that are not used for the control of pests in the raw water

catchment areas.

(iv) If the situation changes or if provider becomes aware of any new information

about the risk posed by any particular parameter, the provider shall, as soon as

practicable, implement monitoring for that parameter at a higher frequency and

also propose further amendment to the water sampling plan.

2.4 Sampling plan for operational monitoring



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(Where necessary, operational monitoring will also form part of the water safety plan.)

The water providers shall carry out sampling of drinking water for the following parameters as

a part of the operational monitoring.

(a) Aluminium: Where aluminium-based coagulants are used in the water treatment

process, the concentration of aluminium shall be tested at least once in a month in the

drinking water.

(b) Conductivity: For water treatment systems that use desalination membrane

technologies, the electrical conductivity of the desalinated water (which may also be

expressed as total dissolved solids as per Appendix A) should be monitored through

on-line analysers, and through manual analysis of grab samples (for cross-checking of

the result of on-line analysers).

(c) Lead and copper: In samples collected from the point of use of drinking water, or from

the water distribution network depending upon the boundary of the responsibility of

the water provider.

(d) pH and turbidity:

(i) These parameters should be tested from the designated sampling locations more

frequently than the parameter, E.coli, mentioned in paragraph 2.2(a), where

required due to risk assessment.

(ii) Monitoring for these two parameters at the water treatment system should ideally

be through on-line analysers unless it is not practical or essential due to the type

of the water supply system and surveillance used by the provider. The on-line

analysers should be calibrated to maintain its consistency and accuracy.

(e) Additional parameters, which are deemed necessary to monitor as a part of the

operational monitoring, preventive measures, water safety plans or as a result of any

contamination of raw water or an event which is likely to affect the quality of drinking

water. These parameters, for which the water provider will propose the frequency of

sampling, may include some of the parameters mentioned in Appendix A of this COP.

2.5 Sampling frequency and parameters

(a) The water provider may select a frequency of sampling higher than that mentioned in

paragraphs 2.2, 2.3 and 2.4, and may even include parameters other than those

specified in the Schedule of the EPH (WSD) (No. 2) Regulations.

(b) Examples of situations where a water provider should select additional parameters

and/or higher frequencies of sampling, in the plan include: Initial monitoring of a new

supply system, epidemiological findings of a waterborne disease, good practices or

remedial actions identified during audits and preparation of water safety plans,



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operational failure, non-compliance of the test result with the standard, adverse

feedback on the quality of water from consumers, or any other unsatisfactory situation.

2.6 Sampling locations and points

(a) All sampling locations shall be such that they can be identified using a location code,

name or address.

(b) Unless otherwise specified, the sampling points shall be, so far as practicable, such

that they can be accessed safely, and the water sample is representative of the part of

the water system or supply being monitored. To achieve this, the water provider may

designate multiple sampling points with backflow prevention devices as necessary.

2.7 Test methods

(a) The test methods6 proposed in the sampling plan by the water provider shall be those

approved by a national accreditation body (e.g. Singapore Accreditation Council), or

those that are based on the procedure(s) issued or endorsed by any international

organization or a regulatory body in another country or others as the Director-General

may allow.

(b) The accuracy, precision and limit of detection offered by the test method shall be

adequate for which the measurement is to be made.

(c) Water providers may propose more than one test method for the parameters included

in the water sampling plan so long as the test methods meet the criteria stated in

paragraphs 2.7(a) and 2.7(b).

2.8 Sampling protocol

The water provider shall adopt an appropriate sampling protocol depending upon the parameter

to be tested.

6 These may include test methods that are developed in-house, or developed by equipment suppliers, e.g. for

on-line monitoring of parameters.



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3.0 Water safety plans

3.1 General

(a) A water safety plan is an effective way to minimize the likelihood of any drinking

water failing to meet the water quality standards.

(b) According to WHO Guidelines, a water safety plan comprises, as a minimum, the

three key components that are the responsibility of the drinking water providers to

ensure that drinking water provided is safe. These are: system assessment; operational

monitoring; and management plans, documentation and communication.

(c) The water safety plans will vary in complexity, as appropriate for the situation, but

their elements shall be based on the multiple-barrier principle, the principles of hazard

analysis and critical control points, and other systematic management approaches.

(d) Preparation and implementation of water safety plan are important steps in the

development of overall strategies for ensuring quality of drinking water. To strengthen

the water safety plan framework, the providers shall also implement measures to

identify, investigate and take remedial actions if any unsatisfactory situation is

identified.

(e) Where applicable, a water provider may also integrate certain parts of the water safety

plan with the other systems implemented within the organization, such as Hazard

Analysis and Critical Control Points (or HACCP), ISO 22000, ISO 9001, etc., to make

the water safety plan more robust.

(f) Each provider shall use a template available from SFA to document the water safety

plan. The plan will include relevant information mentioned in paragraph 2.1, and

details about raw water, water treatment programmes and facilities, water supply

zones/areas, distribution network including service reservoirs and storage tanks,

hazard assessment and risk characterization, sanitary inspection, and other details as

necessary.

3.2 Methodology and key steps

(a) The methodology and the key steps in developing a water safety plan shall be in

accordance with Figure 4.1 and Chapter 4 (“Water Safety Plans”) of the WHO

Guidelines. (For further guidance, the water providers should refer to the Section 4.0,

“References” of this COP.)

(b) The key steps that water providers should follow are outlined in paragraphs 3.3 to 3.10

below.

3.3 Assemble a water safety team

(a) The water provider should form a team to prepare the water safety plan.



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(b) This team should ideally be multi-disciplinary, consisting of a group of stakeholders

that may include managers, engineers, water quality controllers, technical staff

involved in day-to-day operations, etc. Experts from external organizations (including

consultants and contractors) may also participate in the team.

(c) The team should have the knowledge of the water supply system and the types of

safety hazards to be anticipated, and should have the authority to implement the

necessary changes to ensure that safe water is produced and provided.

(d) When a team member leaves the team, it should be ensured that there is a continuity

and proper handing over of the roles and responsibilities with regard to the

development and implementation of the water safety plan.

3.4 Document and describe the system

(a) This should cover the whole system from the source to the point of drinking water

supply, or from the source to the point of consumption if the relevant systems are

owned/operated by the water provider, and should include the various types of source

water, treatment processes, storage and distribution infrastructure, and measures for

source and resource protection.

(b) These descriptions, which can also take the form of flow diagrams, provide an

overview of the supply and an initial understanding of the processes.

3.5 Undertake a system assessment

(a) Conduct a hazard assessment and risk characterization to identify and understand how

hazards can enter into the water supply. (Also assess the existing or proposed system.)

(b) The hazard assessment requires that all potential hazards and hazardous events that

could be associated with the water supply, including the proposed or new water supply

systems, are identified. Such hazard assessment shall also include review of customer

complaints and past events that had affected, or could possibly have affected drinking

water quality, or sufficiency of supplies and, where as a result, there was a risk to the

health of the consumer.

(c) Typical areas that should be taken into consideration include, but not limiting to those

mentioned in Appendix B.

(d) The water provider shall conduct a sanitary inspection of the water supply either as a

part of the hazard assessment or as a part of the verification practice when required,

using a checklist available from SFA (prepared based on Ref. 4(d) or other suitable

guidelines).

(e) Once the potential hazards, their sources and hazardous events are identified, the risk

associated with each hazard or hazardous event should be described by identifying the



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likelihood of occurrence (e.g. almost certain, likely, moderately likely, unlikely and

rare) and severity of consequences if the hazard occurred (e.g. catastrophic, major,

moderate, minor and insignificant). Definitions of likelihood and severity categories

are provided in Tables 4.1 and 4.2 of the WHO Guidelines.

(f) By using a scoring matrix outlined in Table 4.1 of the WHO Guidelines or any other

suitable classification framework, the risk identified as above can be reviewed in order

to establish the significant hazards and hazardous events.

3.6 Identify control measures and define monitoring of control measures

(a) According to WHO Guidelines, the identity and number of control measures (the

means by which risk may be controlled) are system specific and will be determined

by the number and nature of hazards and hazardous events as well as the magnitude

of associated risks.

(b) For the control measures relating to the hazards identified under section 3.5, the water

providers should define monitoring of the control measures (i.e. what limits define

acceptable performance and how these are monitored).

(i) Such monitoring may include process control parameters and water quality

parameters that can be measured, for which limits can be set, and which can be

monitored with sufficient frequency to reveal failures in a timely fashion, and for

which procedures for corrective action can be implemented in response to

deviation from limits.

(ii) Some other examples of operational monitoring parameters that can be used to

monitor control measures can be found in Table 4.3 of the WHO Guidelines.

(c) Where separate procedures for control measures exist, e.g. in the form of equipment

manufacturer’s instructions, SOPs for calibration and maintenance of analysers, etc.,

these can be cross-referenced in the water safety plan, where applicable.

3.7 Verification of water safety plan

(a) Verification provides a check on the overall performance of drinking water supply and

the safety of drinking water being provided by the provider.

(b) The provider shall undertake verification of the water safety plan, which may include

checking or auditing of practices implemented against those documented in the plan,

testing for quality of drinking water as per the water sampling plan, and monitoring

of the water treatment processes and water quality parameters as per section 3.6 of

this COP.

(c) Appropriate quality assurance and analytical quality control measures should also be

implemented for activities linked to verification of water safety plan.



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3.8 Develop supporting programmes

(a) Many actions are important in ensuring drinking water safety, but they do not directly

affect quality of drinking water, and are therefore not “control measures”. These are

referred to as “supporting programmes”, and should be documented in the water safety

plan.

(b) The water provider shall prepare appropriate supporting programmes (e.g. those

relating to security of plant premises, staff training, hygienic work practices, use of

chemicals and materials, etc.) that are necessary to ensure drinking water safety.

(c) With regard to training of staff, apart from the technical training, the provider shall

also implement programmes to train the staff in handling incident situations

mentioned in Section 3.9.

3.9 Prepare management procedures

(a) Water provider shall prepare management procedures (including corrective actions)

for normal and “incident” conditions.

(b) Such procedures shall document actions to be taken in response to variations that

occur during the normal operational conditions, and during specific “incident”

situations where a loss of control of the system may occur, including unforeseen and

emergency situations (e.g. when it is necessary to issue an advisory such as Boil

Water, Do Not Drink or Do Not Use Water, or when a non-compliance with water

quality standards occur).

(c) The actions should spell out communication and notification to the SFA7, media and

consumers/public, and also plans to stop water supply and provide alternative drinking

water, where applicable.

(d) Where any water quality incident occurs that is likely to pose a potential danger to

human health8, the provider shall, as soon as practicable, make reasonable efforts to

inform the members of public or persons to whom the water was sold or supplied,

about the health risk and the measures that should be taken to address the risk, as a

part of remedial measures.

(e) Where necessary, the provider may issue a statement or a notice to the persons and

deliver it through an appropriate mode (e.g. by hand, electronic mail or briefings),

7 Notification to the SFA shall include the 24-hour notification as required under Regulation 9 of the EPH

(WSD) (No. 2) Regulations.

8 Examples of situations that may pose a potential danger to human health include receiving of information

about water borne outbreaks or illnesses arising from consumption of drinking water, or detection of E.coli

in drinking water or detection of pathogens, chemicals or radioactivity at a concentration or value that may

cause illnesses. In assessing the concentration or value, data from testing of water or any other information

or evidence that ascertain the quality of water should be used.



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and/or publish it on the provider’s website, or advertised on a bulletin board nearest

to the place or building where water was provided, or advertised through appropriate

media (radio, television, newspapers, social media).

3.10 Establish documentation and communication procedures

(a) Under a water safety plan, these should include, as practicable, the documentation,

records and communication strategies outlined within Section 4.6 of the WHO

Guidelines, and others that are identified by the provider for effective implementation

of water safety plan.

(b) Communication strategy should include the appropriate procedures mentioned in

sections 3.8 and 3.9 of this COP.

(c) Some of the formats, terms and standard language that can be used for communication

to consumers can be found in Ref. 4.0(g) of this COP.

3.11 Review of the Water safety plan

(a) The review of the water safety plan shall be carried out by the water provider at least

once a year, or when necessary as a result of any major water quality incident or major

upgrading works. During the review, changes in the circumstances from the period

when water safety plan was last prepared and was last reviewed if applicable, shall be

examined.

(b) The water safety plan shall be amended to reflect the relevant changes concerning

Sections 3.3 to 3.10.

3.12 Submission of the report of the review of water safety plan

(a) After the review of the water safety plan, the water provider shall submit to the

Director-General or staff authorized by the Director-General, a report stating whether

the water provider has identified any proposed amendments to the water safety plan.

The report can be in the form of a notification or an e-mail stating the outcome of the

review.

(b) If the water provider has identified any proposed amendments to the water safety plan,

the water provider shall submit a copy of these amendments for approval in the form

and manner prescribed by the Director-General.

3.13 Remedial and improvement measures

The water provider shall take the necessary remedial and improvement measures identified

during the preparation and review of the water safety plan in order to minimize the likelihood

of any drinking water failing to comply with the water quality standards specified in the

Schedule of the EPH (WSD) (No. 2) Regulations.



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4.0 References

Following references are used to prepare this code of Practice. The references are available for

download from the websites of respective organizations.

(a) Guidelines for Drinking-water Quality, Fourth Edition, incorporating the First

Addendum, published by WHO, 2017.

(b) Water Safety Plan Manual: Step-by-step risk management for drinking-water

suppliers”, published by WHO, 2009.

(c) “Water Safety Planning for Small Community Water Supplies: step-by-step risk

management guidance for drinking-water supplies in small communities”, published

by WHO, 2012.

(d) “Water Safety Plans - Managing drinking-water quality from catchment to consumer”,

published by WHO, 2005.

(e) “National Primary Drinking Water Regulations”, published by United States

Environmental protection Agency, Doc. No. EPA 816-F-09-004, May 2009.

(f) “National Secondary Drinking Water Regulation” published by United States

Environmental protection Agency, Doc. No. EPA 816-F-09-004, May 2009.

(g) Code of Federal Regulations, Title 40, “Protection of Environment”, PART 141—

National Primary Drinking Water Regulations, Subpart Q, “Public Notification of

Drinking Water Violations” including “Appendix B to Subpart Q of Part 141—

Standard Health Effects Language for Public Notification”, published by Office of the

Federal Register, United States.

(h) COUNCIL DIRECTIVE 98/83/EC of 3 November 1998, on the quality of water

intended for human consumption, issued by The Council of the European Union, and

its latest amendments including Commission Directive (EU) 2015/1787 of 6 Oct 2015.



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Appendix A: Drinking water parameters

Note

(a) The water provider shall review this Appendix during the preparation of the drinking

water sampling and safety plans and their subsequent reviews, to identify the water

quality parameters that should be monitored as a part of the Operational or

Comprehensive monitoring.

(b) Where applicable, guideline values are provided to assist water providers in

establishing internal control values.

(c) For some parameters, such as copper and manganese, internal control values lower

than the regulatory standards prescribed under the EPH (WSD) (No. 2) Regulations

could be considered based on acceptability or aesthetic aspects (e.g. to prevent

staining of surfaces).

(d) Where the guidelines values are not provided, the provider may adopt a guideline

value based on the historical values (e.g. using 2 Standard Deviations or one order of

magnitude of the mean) for the purpose of identifying an unusual reading.

(e) The list is not exhaustive as drinking water may be contaminated by a number of

contaminants. Hence, as mentioned in sections 2.2 to 2.5, the water provider may

include additional parameters in the water sampling plan, or carry out internal studies,

investigations or surveillance to address any emerging concerns9. Some of these

parameters are described within Chapters 7, 8, 9, 10, 11 and 12 of the WHO

Guidelines.

9 Where applicable, such parameters may include pharmaceutical compounds, endocrine disrupters,

Chromium (VI), synthetic nanoparticles, pesticides, etc., notwithstanding the fact that according to WHO

Guidelines, routine monitoring for pharmaceuticals in drinking water and additional or specialized drinking

water treatment to reduce the concentrations of pharmaceuticals in drinking water are not considered

necessary.



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Parameter Guidance/guideline value Remark

Physico-chemical and chemical

pH Where chlorine is used for

disinfection, the pH should

preferably be less than 8.

However, lower-pH water (pH 7

or less) is more likely to be

corrosive, and hence, corrosion

of materials should be considered

by water provider in setting the

internal control value for pH.

Please refer to the footnote.10

Aluminium11 For processes using aluminium-

based coagulants:

Max. 0.1 mg/litre or less in

large water treatment facilities

that serve 10,000 or more

people12

Max. 0.2 mg/litre or less in

small facilities that serve less

than 10,000 people

Based on practicable levels

considering optimization of the

coagulation process.

Chloride Max. 250 mg/litre

Chlorine dioxide Max. 0.8 mg/litre

Conductivity Max. 1,000 µS/cm (at 25o C) Based on guideline value for

total dissolved solids, where

applicable

10 pH of water should be controlled during the water treatment process to ensure satisfactory coagulation,

flocculation, clarification and disinfection of water where applicable. The pH of drinking water entering the

distribution system must be controlled to minimize the corrosion of water mains and pipes in household

water systems. Extreme values of pH (less than 3 or more than 12) can result from contamination or

accidental spills, treatment breakdowns or lapse, and insufficiently cured cement mortar pipe linings or

cement mortar linings applied when the alkalinity of the water is low. Control measures should be established

to prevent such extreme values of pH of water.

11 For all drinking water treatment involving aluminium, a health-based value of max 0.9 mg/l is

recommended under WHO guidelines (Ref 4.0 (a)).

12 Where data on estimated population served are not available, the provider may use the data on Singapore's

per capita domestic water consumption or such other information, and may exclude the quantity of water

used for non-potable applications, in order to set the guideline value.



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Foaming agents

Max. 0.5 mg/litre

Hydrogen sulfide Taste and odour thresholds in

water are estimated to be

between 0.05 and 0.1 mg/litre

Please refer to parameter “Taste

and odour” in this Table, below.

Iron Max. 0.3 mg/litre

Taste and odour Water should be free of tastes

and odours that would be

objectionable to the majority

of consumers.

For odour: 3 threshold odour

number

Please refer to the footnote13

Silver

Max. 0.1 mg/litre

Sulfate

Max. 500 mg/litre

Total Dissolved

Solids14

Max. 600 mg/litre

Turbidity Max. 0.3 NTU for water after

filters15

Max. 1.0 NTU for water after

end of entire treatment process

Max. 5.0 for water at the

consumer’s tap

To minimize the risk of

cryptosporidium in drinking

water, particular consideration

should be given to any abnormal

increase in the turbidity levels.

Zinc

Max. 5 mg/litre

Microorganisms and parasites

Heterotrophic plate

count (also called as

colony count by some

laboratories)

Max. 500 cfu/millilitre

13 Objectionable taste or odour may create concerns about the quality and acceptability of a drinking water

supply. The concentration at which constituents are objectionable to consumers is variable. Tastes and

odours may be detectible by consumers at lower or higher levels of the guideline values or regulatory

standards, depending on individual and local circumstances.

14 Parameter, total dissolved solids, is sometimes estimated using the result of electrical conductivity of water

by multiplying the conductivity reading in µS/cm by a factor of 0.67.

15 To minimize the risk of Cryptosporidium and such other microbial contaminants in drinking water.



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Total coliform16,

Cryptosporidium17,

Giardia18,

Legionella19, and

other relevant

organisms

Public health goal for these

micro-organisms and pathogens

should be “zero” or <1 cfu per

sample volume specified by the

standard test method used.

Radiological parameters

If either of the gross

Alpha or Beta level is

exceeded above the

level of 0.5 Bq/litre or

1 Bq/litre

respectively, the

specific radionuclides

should be identified

and individual

activity

concentrations

measured20.

Guidance levels for individual

radionuclides in Bq/litre - as

per WHO Guidelines or other

international guidelines

Individual dose criterion/IDC

(or total indicative dose) equal

to 0.1 mSv/year should not be

exceeded, based on the criteria

provided in Ref. 4.0(a)21.

16 Total coliform bacteria include a wide range of aerobic and facultatively anaerobic organisms that can

survive and grow in water. They are not useful as an indicator of faecal pathogens, but they can be used

as a disinfection indicator, and to assess the cleanliness and integrity of distribution systems and the

potential presence of biofilms. [Ref. 4.0(a)]

17 Cryptosporidium is a parasite; whose oocysts are extremely resistant to chlorine. Ideally, control

measures to reduce potential risk from Cryptosporidium should focus on prevention of source water

contamination by human and livestock waste (with particular attention to cattle/farm animals), adequate

treatment of water, and protection of water during distribution.

18 Giardia is a parasite, whose cysts are more resistant than E. coli bacteria to chlorine, but they are not as

resistant as Cryptosporidium. Usually, same control measures, as those mentioned for Cryptosporidium

should apply for Giardia.

19 Legionella are waterborne bacteria that may survive and grow in biofilms and sediments. If testing for

Legionella is carried out, the ISO 11731 or equivalent method should be used. Where instances of

Legionella being detected, it is recommended to identify/quantify the species and serogroup(s) of

Legionella detected in the sample.

20 Although iodine and tritium will not be detected by standard gross activity measurements and routine

analysis for these radionuclides is not necessary, if there are any reasons for believing that they may be

present, radionuclide specific sampling and measurement techniques should be used.

21 IDC = Guidance level of radionuclide (Bq/litre) X dose coefficient for ingestion by adults (mSv/Bq) X

annual ingested volume of drinking water, assumed to be 730 litres/year. For Guidance levels and dose

coefficients of radionuclides, please refer to Table 9.2 and Annex 6 of the Ref. 4.0(a), or other

international guidelines.



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Appendix B: Factors and hazards that should be considered during the preparation of

water safety plan

Note

(a) A list of common factors and hazards is shown below. These factors and hazards

should be addressed in the water safety plan, where applicable. The list is non-

exhaustive as it is not possible to include all the factors and hazards in this Appendix,

due to the diverse and wide-ranging nature of the water treatment and distribution

systems used by various water providers.

(b) A multi-barrier approach in the water treatment process and distribution should be

adopted, so as to ensure consistent quality and safety of drinking water.

(1) Source and raw water (including catchment areas, reservoirs, etc.)

(a) Likelihood of water contamination due to:

(i) Industrial discharges

(ii) Accidental oil/chemical spills

(iii) Illegal discharge of silt-laden water from construction sites

(iv) Leakage from sewage pipes or septic tanks

(v) Activities within the catchment area and reservoir from animals and humans

(recreational activities, farm activities, fogging, fireworks, horticulture,

irrigation, littering, etc.)

(vi) Air pollution from nearby sources or transboundary haze

(vii) Natural events (earthquake, rainstorm, etc.) and seasonal variations

(viii) Climate change

(b) Associated risk of algal and cyanobacteria blooms. Control of algal and cyanobacteria

blooms in the reservoirs and waterways through physical, chemical and biological

measures.

(c) Sources mentioned in paragraph 1(a) that may contaminate the water by chlorine

resistant microorganisms such as Cryptosporidium.

Note

Risk assessment for Cryptosporidium based on raw water quality and treatment

programme should be incorporated in the water safety plan either separately or as a part



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of “Hazard assessment and risk characterization”.

(2) Water treatment system

(a) Inadequate physical security measures implemented at the site.

(b) Inadequate disinfection of water.

Note

For effective disinfection with chlorine, there should be a residual concentration of

free chlorine of ≥0.5 mg/litre after at least 30 minutes of contact time (or equivalent

based on concentration X time value) at pH<8.0.

(c) Failure or malfunction of plant and laboratory equipment (including on-line analysers,

piping connections and equipment parts).

Note

A treatment work should ideally shut down automatically almost immediately after a

disinfection failure is detected through appropriate alarms; or procedures should be in

place for a treatment work to be manually shut down almost immediately after an

appropriate alarm warning of a failure of adequate treatment and disinfection. A

provider should install such alarm systems or implement alert procedures.

(d) Use of plumbing materials including liners which are not suitable for potable water

(e.g. those that do not comply with Singapore Standard 636, “Code of Practice for

Water Services” and those that do not comply with the guidelines or standards

issued by the Public Utilities Board, Singapore).

(e) Media/sand filter breakthrough leading to problems such as poor quality of filtered

water, including presence of micro-animals in filtered water. Also, build-up of

biofilms /algae/flotsam on sand filter/other surfaces.

(f) Deterioration of the membrane in plants that use membrane treatment plant.

(g) Over/ under dosing of chemicals such as fluoride, chlorine, lime, alum, ozone,

polymer and ammonia.

(h) Improper use of chemicals or use of chemicals that are of unacceptable purity.

Note

(i) One of the control measures shall involve the use of only those water treatment

chemicals for the production of drinking water, which are certified by the

manufacturer, supplier, independent laboratory or a national or international

authority to have conformed to the required purity.



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(ii) Water provider should require the vendor of chemicals to provide Certificate of

Analysis or Certificate of Quality with each delivery of the chemicals, and

compare the test results with the relevant specifications.

(iii) Water treatment systems that use polymers should ensure that concentrations of

residual monomers, Acrylamide and Epichlorohydrin, in the drinking water are

calculated according to the product specifications of the maximum release from

the corresponding polymers, Polyacrylamide and Polyamines, in contact with the

water, for comparison with the standards prescribed under the Schedule of the

EPH (WSD) (No. 2) Regulations.

(i) Improper storage of water treatment chemicals leading to contamination of chemicals

and compromising workplace safety.

(j) Unauthorized access to any bypass line in the treatment process that may allow water

to bypass a treatment stage.

(k) Contamination of water storage tanks through air vents, overflow pipe, etc. (e.g.

during fogging and such other activities carried out near the vents).

(l) Build-up of trihalomethanes (THMs) in water storage tanks or clear water tanks during

operation.

(m) Power/electricity failure and risk of fire, explosion and lightning at the plant resulting

in interrupted treatment and loss of disinfection of water.

(3) Distribution network and water service installations within buildings/facilities

(where applicable)

(a) Intrusion of contaminants in service reservoir and storage tanks (due to cracks/defects

in walls, fogging, sabotage, intrusion by small animals, etc.).

(b) Leaching of contaminants in water from new mains/pipes that may affect pH of water.

(c) Inadequate maintenance (cleaning and disinfection of service reservoir and water

storage tanks).

(d) Intrusion of contaminants in water due to pipe burst, pipe failures, corrosion of

plumbing materials, leaking joints and adapters, cracks in pipelines and deficient

seals.

(e) Opening/closing of valves, firefighting or testing of fire hydrants that may result in

pressure fluctuations and suspension of sediments, causing discoloured water.

(f) Stagnant water in mains that may result in high pH, high turbidity, discoloured water

or biofilms.



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(g) Inadequate residual disinfectant in the distribution system.

(h) Accidental or illegal connections of piping network.

(i) Security measures for water storage tanks in buildings not meeting the minimum

stipulated security requirements in the Public Utilities Act, Public Utilities (Water

Supply) Regulations and SS 636:2018.

(j) Inadequate backflow prevention of water towards source of supply from any tank or

appliance.

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